The present invention relates generally to a vehicle drive-train system utilizing a master friction clutch and, in particular, to a centrifugal master friction clutch including a means for installing the clutch in the drive-train system.
Vehicle drive-train systems that comprise an internal combustion engine, a master friction clutch and a transmission are known in the art. Typical master friction clutch assemblies generally include a cover assembly comprising a pressure plate, a cover and a diaphragm spring, all coupled for rotation together with an engine flywheel. More precisely, a typical master friction clutch also includes at least one friction plate, commonly called a driven disc, having at its outer periphery friction pads and at its inner periphery a hub that is mounted on a driven member, such as a transmission input shaft. When the clutch is disengaged, the pressure plate is axially removed from the friction plate and no torque is transferred between the engine flywheel and the friction plate. When the clutch is engaged, the pressure plate supplies a clamping force against the friction plate causing the engine flywheel and friction plate to contact and transfer torque therebetween.
Common state of the art vehicle master friction clutch assemblies are normally closed (engaged) systems that generally include a release member, such as a bearing mechanism, to selectively disengage the clutch under direction of the vehicle operator. A procedure for installing normally closed clutch systems in a vehicle drive-train system typically includes: (i) installing the friction plate(s) on a temporary installation shaft; (ii) securing the clutch cover assembly to the flywheel to clamp the friction plate(s) between the flywheel and a pressure plate; and (iii) removing the installation shaft to permit insertion of a transmission input shaft. The friction plate(s) are held in position after removal of the installation shaft by the clamping force of the pressure plate until the transmission can be installed into the vehicle drive-train system.
Normally open (disengaged) vehicle master friction clutch systems, such as centrifugally operated friction clutches, are also well known in the art. Centrifugally operated friction clutches generally include an input member driven by an internal combustion engine and weights pivotable with respect to the input member which, upon rotation of the input member, will rotate or pivot radially outwardly under the effect of centrifugal force to cause the input member to frictionally engage an output member. An example of a centrifugally operated friction clutch may be seen by reference to pending U.S. patent applications Ser. Nos. 09/813,494; 09/813,919; and 09/814,494, filed Mar. 21, 2001, which are owned by the assignee of the present invention and are hereby incorporated by reference in their entirety.
Unlike a normally closed (engaged) master friction clutch system, the pressure plate in a normally open (disengaged) master friction clutch system does not exert a clamping force on the friction plate(s) until the clutch is engaged. Accordingly, securing the clutch cover assembly of a normally open master friction clutch system to the engine flywheel does not clamp the friction plate(s) between the flywheel and the pressure plate. The inability to adequately secure the friction plate(s) after removal of the installation shaft renders a conventional normally open clutch system difficult to install in a vehicle drive-train system.
In accordance with an embodiment of the present invention, a normally open, centrifugal master friction clutch is provided, which includes a device that facilitates installation of the master friction clutch into a vehicle drive-train system. In a preferred embodiment, the master friction clutch includes an input portion fixed for rotation with an engine flywheel and an output portion fixed for rotation with a transmission input shaft. The output portion comprises at least one friction plate secured to the transmission input shaft for rotation therewith. The input portion includes a cover assembly secured to the engine flywheel for rotation therewith. The cover assembly comprises a pressure plate for applying a clamping force against the friction plate(s), a plurality of flyweights that pivot outward under the effects of centrifugal force to cause the pressure plate to exert a clamping force against the friction plate(s), and a clutch installation device.
The clutch installation device comprises a first member rotatably disposed in the cover assembly radially inwardly of the flyweights and a second member adjacent the first member for engagably limiting the degree of rotation of the first member. The first member of the inventive clutch installation device includes at least one cam lobe for engaging at least one of the flyweights during rotation of the first member relative to the second member. The rotating cam lobe forces the engaged flyweight to rotate outward to modify the position of the pressure plate, such that, when the cover assembly is secured to the engine flywheel, the pressure plate provides a clamping force against the friction plate to prevent movement thereof.
In a preferred embodiment, the first member is slidably disposed on a shaft-like structure of the second member. The first member further includes a first inclined cam surface against which a second inclined cam surface of the second member acts to convert rotative movement of the first member relative to the second member into axial movement. The second member further includes a slot proximate the second cam surface that is configured to receive a lug on the first member to limit the degree of rotation of the first member relative to the second member.
In a second embodiment, the second member is disposed on a land of the first member. An inner surface of the second member includes a plurality of slots that receive a plurality of corresponding tabs located on the first member. During rotation of the first member, each tab engages a surface of a corresponding slot to limit the degree of rotation of the first member relative to the second member.
In a third embodiment, the second member is disposed on a land of the first member. The first member includes a plurality of inclined cam surfaces against which corresponding cam members on the second member act to convert rotative movement of the first member relative to the second member into axial movement. The second member further includes a plurality of tabs that are each configured to engage a corresponding lug on the first member to limit the degree of rotation of the first member relative to the second member.
Among other advantages, the inventive clutch installation device simplifies installation of a normally open, centrifugal clutch system enabling a centrifugal master friction clutch to be easily installed into a vehicle drive-train system. The inventive clutch installation device prevents movement of clutch friction plate(s) during installation of a normally open, centrifugal master friction clutch into a vehicle drive-train system. The inventive clutch installation device provides a means of easily xe2x80x9cunlockingxe2x80x9d the device after installation of the clutch into the vehicular drive-train system. The inventive clutch installation device advantageously blocks the ingress of contamination into the area surrounding the centrifugal flyweights to promote reliable operation of the centrifugal components of the clutch.
Various additional aspects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.